An ink jet recording method is a system wherein liquid ink is directly ejected to a recording medium such as paper, plastic sheet or others to record a letter or an image. This method is advantageous in apparatus used therefor in that it is easily adaptable for the color printing and capable of being smaller in size since the mechanism is simple, or low in noise. Also, since this system uses no form plate, it is possible to readily obtain a stable print from the beginning. Further, the recent ink jet printer can output an image having a high quality grade equal to that of silver salt photograph at a high speed, whereby it has widely been used in homes or offices.
One of the problems of the ink jet recording system is in that the quality grade of the image is different between used recording media. This is because the fixing of the ink is relied upon the permeation thereof to the recording medium. Recently, the demand has been increased particularly in the industrial field in that high-grade images are output irrespective of kinds of a recording medium, and becomes a serious problem in the ink jet recording system.
For instance, in the recording medium having the excessively high ink permeability, a phenomenon called as feathering may occur wherein ink blurs along fibers of paper. Also, there may be an inconvenience in that colorant sinks together with water in the ink whereby the color development becomes worse or an image formed on a front surface is visible from a rear surface. If the ink-permeability of the recording medium is less, there may be a phenomenon called as beading wherein adjacent ink dots are attracted together, that called as bleeding wherein inks are mixed together in a boundary between different color areas or a case wherein printed ink does not dry for a long time. These problems are caused by a high fluidity of ink used for the ink jet recording system.
An ink ejection system in the ink jet recording system includes, other than a continuous system, an on-demand system using an electro-thermal transducer element (heating element) or an electro-mechanic transducer element. In either system, it is impossible to eject ink other than that having a low viscosity. This is because ink used in the ink jet recording system must have high fluidity within the ink jet head for satisfying the ejection suitability. On the contrary, as described before, the ink is required for having low fluidity on the surface of the recording medium so that the adjacent ink drops are not mixed together or attracted to each other. As mentioned above, in the ink jet recording system, in spite of ejecting ink having high fluidity to the recording medium, the fluidity thereof must be lowered on the recording medium; in other words, opposite characteristics are required.
To simultaneously satisfy such requisites opposed to each other, it has been proposed that an ink image is formed on an intermediate transfer body, and transferred to a desired recording medium to record the ink image thereon (see the United States Patent Nos. 4,538,156 and 5,099,256 and Japanese Patent Laid-Open No. 62-92849(1987)). In these systems, the ink ejected from the ink-jet head is once adhered to the transfer body so that an ink image wherein the fluidity of the ink is lowered to some extent is formed on the transfer body, which image is then transferred from the transfer body to the recording medium.
In this method, however, while it is premised on the assumption in that the ink image having no disturbance is formed on the surface of the intermediate transfer body, the surface of the intermediate transfer body used therefor is not ink-absorbable in view of the cleanability by taking the repeated uses into account and/or the transferring ability to the recording medium. Accordingly, the beading and/or the bleeding are liable to occur on the surface of the intermediate transfer body.
In Japanese Patent Publication No. 2916864 and Japanese Patent Laid-Open No. 2002-321350, a method has been proposed wherein liquid reactive to ink is coated on the intermediate transfer body, so that when the ink is in contact with this liquid, the two liquids are reacted to control the ink fluidity. It is said that if this method is adopted, the beading and/or the bleeding are prevented from occurring on the surface of the intermediate transfer body, whereby a favorable image is obtainable.
In this case, however, since ink drops are applied to the intermediate transfer body via a layer of the reactive liquid, the image quality is largely influenced by a state of the reactive liquid applied to the transfer body. That is, if the reactive liquid is not properly applied to the intermediate transfer body to form a thin layer having a uniform thickness, the landing deviation of ink drop or the deformation of dot shape may occur to disturb the formation of a high grade image on the intermediate transfer body and thus the recording of a high quality image on the recording medium.